The rapid development of digital communication systems raises a higher demand to the reliability of the data communication, however, under poor channel conditions, especially under high data rate or mobile environments, the phenomena such as multi-path interference and Doppler shift greatly affect the performance of these systems. Therefore, effective error control techniques-especially Hybrid Automatic Repeat Request (HARQ)-have became a research hotspot in the field of communication.
In the downlink HARQ of a Long Term Evolution (LTE) system, a HARQ Acknowledgement (HARQ-ACK) of a Physical Downlink Shared Channel (PDSCH) will be transmitted over a Physical Uplink Control Channel (PUCCH) when a User Equipment (UE) has no Physical Uplink Shared Channel (PUSCH), wherein the HARQ-ACK can comprise the following three states: acknowledgement (ACK), negative acknowledgement, and discontinuous transmission (DTX) respectively.
In a present LTE system, the Physical Uplink Shared Channel can support multiple uplink control signaling, including the above HARQ-ACK and Periodic Channel State Information (P-CSI), wherein the P-CSI may include Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI) and Rank Indicator (RI), Scheduling Request (SR) and their combinations when being transmitted simultaneously.
The LTE defines multiple PUCCH formats, including: PUCCH format 1/1a/1b (its structural schematic diagram is shown in FIG. 1) and format 2/2a/2b (its structural schematic diagram is shown in FIG. 2), wherein the format 1 is used for transmitting the scheduling requests of the UE, format 1a and 1b are used respectively for feeding back 1-bit HARQ-ACK and 2-bit HARQ-ACK, format 2 is used for transmitting the downlink P-CSI, format 2a is used for transmitting the P-CSI and 1-bit HARQ-ACK, and format 2b is used for transmitting the P-CSI information and 2-bit HARQ-ACK.
In a frequency division duplex (FDD) system of the LTE system, since there is a one-to-one correspondence between the uplink and downlink sub-frames, the UE will feed back 1-bit HARQ-ACK when the PDSCH comprises only one transmitting block; and the UE will feed back 2-bit HARQ-ACK when the PDSCH comprises two transmitting block. Therefore in a LTE FDD system, in the case of the UE needing to simultaneously transmit the SR and HARQ-ACK, the UE transmits 1-bit or 2-bit HARQ-ACK on the HARQ-ACK PUCCH resource allocated to it if it is necessary to transmit the negative SR (this indicates no scheduling request); the UE transmits 1-bit or 2-bit HARQ-ACK on the SR PUCCH resource allocated to it if it is necessary to transmit the positive SR (this indicates to make a scheduling request); and in the case of the UE needing to simultaneously transmit the HARQ-ACK and CSI information, if a sub-frame is a normal cyclic prefix, 1-bit or 2-bit HARQ-ACK are modulated to the second reference signal of each slot and transmitted the 1-bit or 2-bit HARQ-ACK by using the PUCCH format 2a/2b, and if the sub-frame is an extended cyclic prefix, 1-bit or 2-bit HARQ-ACK and P-CSI are encoded jointly and transmitted the encoded 1-bit or 2-bit HARQ-ACK and P-CSI by using the format 2.
However in a Time Division Duplexing (TDD) system of the LTE, there is no one-to-one correspondence between the uplink and downlink sub-frames, and a uplink sub-frame sometimes needs to feed back the HARQ-ACKs of a plurality of downlink sub-frames according to the configuration of different uplink and downlink sub-frames, wherein the plurality of downlink sub-frames corresponding to the uplink sub-frame are called as a bundling window, and a size of the bundling window can be defined as M. In addition, in the LTE system, two HARQ-ACK feedback modes are further defined: one of them is a bundling mode, the core idea of which is to perform a logic and operation on the HARQ-ACKs of transmitting blocks corresponding to each of the downlinks sub-frames needed to be fed back on the uplink sub-frame, and if a downlink sub-frame has two codeword streams, the UE will feed back 2-bit HARQ-ACK; and if each of the downlink sub-frames has only one word stream, the UE will feed back 1-bit HARQ-ACK; and the other one is a multiplexing mode (also known as multiplexing with channel selection), the core idea of which is to utilize the different PUCCHs and the different modulation symbols on these channels to denote the different feedback states of the downlinks sub-frames needed to be fed back on the uplink sub-frame, and if there are multiple word streams on the downlink sub-frames, before selecting the channel, a spatial logic and operation (also known as spatial bundling) can be performed firstly on the HARQ-ACKs fed back by the multiple word streams of the downlink sub-frames, and then they are transmitted by using the PUCCH format 1b. Namely, the HARQ-ACKs after the logic and operation is represented by 2-bit information b(0) and b(1) carried by the PUCCH format 1b and an index of the PUCCH channel.
Therefore in the TDD system, when the HARQ-ACKs need to be transmitted simultaneously together with the SR or P-CSI, the transmitting mode thereof is different from that of the foregoing FDD system. When the HARQ-ACK needs to be transmitted simultaneously together with the SR or CQI, the UE performs a spacial bundling on a plurality of HARQ-ACKs in the bundling window to obtain the HARQ-ACKs corresponding to each of the downlink sub-frames, acquires the corresponding 2-bit information b(0), b(1) according to the number of ACKs after the spacial bundling in the bundling window, and then transmits b(0), b(1) over the PUCCH corresponding to the SR (when the positive SR is transmitted simultaneously), or transmits b(0), b(1) on the PUCCH format 2 after b(0), b(1) are modulated on a second reference signal of the PUCCH format 2b or after b(0), b(1) and P-CSI are jointly coded (the latter two cases are corresponding to the scenario of simultaneous transmission of the P-CSI and HARQ-ACK), wherein there is a preset mapping relation between the number of ACKs after the spacial bundling processing in the bundling window and b(0), b(1), as shown in Table 1:
TABLE 1The mapping relation between the number of ACKs after the spacialbundling processing in the bundling window and b(0), b(1)The number of ACKs after the spacial bundlingprocessing in the bundling windowb(0), b(1)0 or none0, 0(The UE detects that at least one downlinkallocation is lost)11, 121, 030, 141, 151, 060, 171, 181, 090, 1
In an International Mobile Telecommunications-Advanced (IMT-Advanced) system, it can realize the high-speed data transmission and has more system capacity, and in the case of low-speed movement, hot-spot coverage, the peak rate of the IMT-advanced can reach 1 Gbit/s, while in the case of high-speed movement, wide-area coverage, the peak rate of the IMT-advanced can reach 100 Mbit/s.
In order to satisfy the requirements of international telecommunication union-advanced (ITU-Advanced), a long term evolution advanced (LTE-A) system, as an evolution standard of the LTE, is required to support greater system bandwidth (up to 100 MHz) and backwards compatible with the existing standard of the LTE. Based on the existing LTE system, the bandwidth of a LTE system can be combined to obtain a wider bandwidth, which is called as a Carrier Aggregation (CA) technology, and the technology can improve the spectrum efficiency of the IMT-Advanced system and relieve the shortage of spectrum resources, thereby optimizing the utilization of the spectrum resources. Therefore the system bandwidth of LTE after carrier aggregation can be regarded as component carriers, each of which can also be called as a serving cell, namely a spectrum can be aggregated by n component carriers (cells). For the case that the resource of a UE is composed of a plurality of serving cells in frequency domain, one cell therein is called as a primary serving cell, and the others are called as secondary serving cells. After introducing the carrier aggregation technology, a downlink component carrier corresponds to a PDSCH transmitting block and a HARQ process when a space division multiplexing is not adopted, namely the UE needs to feed back 1-bit HARQ-ACK for the PDSCH transmitting block of each of the component carriers. However, when adopting the space division multiplexing, at most 2 transmitting blocks are support under current rules of LTE-A. Therefore in this case, the UE needs to feed back 2-bit HARQ-ACK for 2 PDSCH transmitting blocks of the downlink component carriers.
In a LTE-A system adopting the carrier aggregation technology, the uplink bandwidth and the downlink bandwidth thus can comprise a plurality of serving cells. When the base station has the PDSCH scheduled to a certain UE on multiple downlink component carriers, and when there is no PUSCH to be transmitted by the UE on the current sub-frame, the UE needs to feed back the HARQ-ACK transmitted by the PDSCH of the multiple downlink component carriers on the PUCCH. It is ruled in the related arts that all uplink control information, including SR, HARQ-ACK and P-CSI, are all transmitted on the primary serving cell.
In the LTE-A system, for the SR information, the UE adopts the PUCCH format 1 to transmit, and for the HARQ-ACK, besides the PUCCH format 1a and 1b and multiplexing with channels selection already defined in the LTE, one new format based on DFT-s-OFDM is added to LTE-A in order to transmit the HARQ-ACK with more load, and its structural schematic diagram is shown in FIG. 3. For ease of description, this structure can be called as PUCCH format 3, wherein adopting which mode to feed back the HARQ-ACK in the UE can be configured by the higher-layers. For the P-CSI, although the UE possibly needs to transmit the P-CSI of a plurality of downlink serving cells on a uplink sub-frame, in view of the fact that the case of carrier aggregation is mainly considered for aggregation of two serving cells in an initial version (hereinafter called as Rel-10) of the LET-A, it can be avoided for the UE to transmit the P-CSI of a plurality of serving cells in a same sub-frame so long as eNB is configured rationally. Namely in the Rel-10, the simultaneous transmission of the P-CSI of a plurality of serving cells is not supported. When a sub-frame needs to be transmitted on a plurality of uplink sub-frames, a corresponding priority principle is defined in the Rel-10 for the P-CSI, so that the UE can select a P-CSI with highest priority and transmit it according to the priority principle.
In the Rel-10, the following types of P-CSI reports are defined concretely:
Type 1: supporting the feedback of sub-bands CQI selected by the UE;
Type 1a: supporting the feedback of sub-bands CQI and the second PMI;
Type 2, Type 2b and Type 2c: supporting the feedback of broadband CQI and PMI;
Type 2a: supporting the feedback of broadband PMI;
Type 3: supporting the feedback of RI;
Type 4: supporting the feedback of broadband CQI;
Type 5: supporting the feedback of RI and broadband PMI;
Type 6: supporting the feedback of RI and PTI.
The priority of the above types of P-CSI reports is as following:
for a same serving cell, the priorities of report types 3, 5, 6 are higher than those of reports 1, 1a, 2, 2a, 2b, 2c, or 4;
for the different serving cells, the priorities of report types 3, 5, 6, 2a of a serving cell are higher than those of report types 1, 1a, 2, 2b, 2c, or 4 of another serving cell; and
for the report types with a same priority, the priority of the P-CSI report type with a smallest index value in their corresponding serving cells is highest.
In addition, in the Rel-10 system, the UE also does not support the transmission of the HARQ-ACKs and P-CSI of a plurality of serving cells on an uplink sub-frame, the reason of which is same as above and no more repeat here. Since a typical case of carrier aggregation of the Rel-10 aims to two serving cells, it can be avoided for the UE to simultaneously transmit the HARQ-ACKs and P-CSI of a plurality of serving cells by means of a reasonable schedule, and if a collision occurs, according to the related rules in the Rel-10, the P-CSI are discarded and only HARQ-ACKs are transmitted.
However in a subsequent version (hereinafter called as Rel-11) of the LTE-A, the number of serving cells participating in aggregation is not limited to 2, and therefore the probability of collision of the P-CSI of a plurality of serving cells and collision between the HARQ-ACKs and P-CSI of a plurality of serving cells becomes increasingly higher. If a strategy of discarding the P-CSI with low priority or directly discarding the P-CSI of all serving cells ruled in the Rel-10 is adopted still, this may cause that the CSI information will be not fed back timely, thereby affecting the downlink scheduling and downlink throughput performance. Therefore in the Rel-11, two research goals of enhancing the uplink control signaling are presented: whether to support the simultaneous transmission of the P-CSI of a plurality of serving cells on a sub-frame; and whether to support the simultaneous transmission of the HARQ-ACKs and P-CSI of a plurality of serving cells. Meanwhile in the Rel-11, a Coordinated Multi-Point Transmission and Reception (CoMP) technology is introduced, and in a system with the CoMP being introduced, the P-CSI needed to be transmitted will also increases correspondingly, and the resource of each Channel State Information-Reference Signal (CSI-RS) corresponds to a P-CSI. In the following scenes without otherwise specified, the P-CSI of a plurality of serving cells comprise both the P-CSI of a plurality of serving cells in a carrier aggregation system and a plurality of P-CSI corresponding to a plurality of CSI-RS resources under a serving cell in a CoMP system.
Currently, in term of enhancement of the uplink control signaling, the conclusion is as following:
In the Rel-11, the simultaneous transmission of the P-CSI of a plurality of serving cells on a sub-frame is supported. For a UE supporting the PUCCH format 3, the UE can simultaneously transmit the HARQ-ACKs of a plurality of serving cells, 1-bit SR and the P-CSI of a serving cell on the PUCCH format 3. For how to support the simultaneous transmission of the P-CSI of a plurality of serving cells on a sub-frame, the uplink channel format in the related arts is needed only in terms of the conclusion presently available, but which channel format will be used has not been determined, and there are only two alternatives, including: PUCCH format 3 and PUSCH. If the PUCCH format 3 or PUSCH is introduced in the Rel-11 to support the transmission of P-CSI of a plurality of serving cells on a sub-frame, a problem existing in the related arts lies in how to indicate the resource and how to support the simultaneous transmission of the HARQ-ACKs and P-CSI of a plurality of serving cells.